Heck, one can wet sand it to "leak" the pigments with nothing other than cold water!
If this is what I think you are saying you may not be letting the paint dry enough before sanding. If fully dry you will only have a dry powder from the laquer that will not bleed the color. If the paint has a retarder it could take as much as a week to dry that much. But most spray can laquers only have enough retarder to prevent moisture from fogging in average humidity, this causes the paint to discolor.